Field of the Invention
The invention relates to a configuration for triggering a personal protection system with a trigger signal as a function of a response signal and a release signal, including an acceleration sensor supplying the response signal, a control unit supplying the release signal, a protection device having two switching units each with a fixed electrode and a switching arm interacting with the latter for supplying a closing signal as a function of acceleration, the protection device outputting the trigger signal as soon as both switching units close simultaneously, and a test device associated with the switching units for adjusting the switching arm of each switching unit to a response position as a function of an assigned electrical test signal.
A "personal protection system" is understood herein to be, for example, an airbag system and/or a seat belt pretensioning device.
In order to protect against misfirings of such personal protection systems, it is customary to not only make the triggering dependent on the response signal of an acceleration sensor, but in addition, a release signal of a protection device is necessary. The device is usually a mechanical switch (safing sensor) that operates acceleration-dependently. For example, German Utility Model G 90 01 803.6 U1 discloses a configuration with two mechanical crash sensors as a protection device and an electronic acceleration sensor. In order to carry out a functional test, each sensor is disconnected from the rest of the circuit through the use of controllable switching transistors, something which requires a large degree of outlay for a control device and a switching device.
U.S. Pat. No. 5,085,464 proposes a mechanical switch which operates acceleration-dependently and in which a soft-magnetic seismic mass is connected to a switching arm of the switch. The seismic mass is surrounded by a coil. When current flows through the coil, the switch is held in the open or closed state by the magnetic force acting on the seismic mass, depending on the direction of the flow of current in the coil. However, such a switch which operates acceleration-dependently has not been adopted in practice due to its complex structure and due to its large electromagnetic radiation, which may in turn act on an electronic acceleration sensor of a personal protection system.
German Published, Non-Prosecuted Patent Application DE 38 05 161 A1, corresponding to U.S. Pat. No. 4,991,682, discloses an acceleration sensor device having a plurality of switches which operate acceleration-dependently and have a different response threshold. The individual switches are disposed on a common substrate in that device.